Susceptibility and intra-species transmission of the H9N2 G1 prototype lineage virus in Japanese quail and turkeys Francesco Bonfante 1, *, Livia Victoria Patrono 1 , Roberta Aiello, Maria Serena Beato, Calogero Terregino, Ilaria Capua OIE/FAO Reference Laboratory for Newcastle Disease and Avian Influenza, Department of Comparative Biomedical Sciences, Istituto Zooprofilattico Sperimentale delle Venezie, Legnaro, Padova, Italy 1. Introduction The first appearance of H9N2 influenza A viruses in Asian land-based poultry dates back to 1988, Hong Kong (Perez et al., 2003). Since then, H9N2 viruses of the Eurasian lineage spread across Asia, The Middle East, Eastern Europe and Africa, becoming endemic in several poultry species of many countries (Fusaro et al., 2011; Wan et al., 2008). The circulation of these viruses has been associated in chickens with reduced egg production, mild respiratory distress and low mortality rates (Guo et al., 2000; Kim et al., 2006), although infections in an experimental setting have rarely recorded clinical signs after infection of naı ¨ve birds (El-Zoghby et al., 2012; Gharaibeh, 2008). Nevertheless, in several countries the economic impact of recurrent epidemics has resulted in the adoption of vaccination programmes against H9N2 viruses (Lee et al., 2011; Naeem and Siddique, 2006). Of the distinct lineages circulating in Asia, G1 and Y280 are considered to be dominant in poultry (Fusaro et al., 2011). Evidence of intra and inter-subtype reassortments (Iqbal et al., 2009; Peiris et al., 2001), sporadic infections of mammals and humans (Kim et al., 2006), along with the acquisition of human virus-like receptor specificity (Cong et al., 2007), have led the scientific community to believe H9N2 viruses may have the potential to ignite a pandemic. During the last two decades, South and East Asia have experienced an unprecedented economic transformation. Intensive integrated poultry production partially replaced Veterinary Microbiology xxx (2013) xxx–xxx A R T I C L E I N F O Keywords: H9N2 Quail Turkey Influenza LPAI A B S T R A C T Avian influenza viruses of the H9N2 subtype have circulated in the poultry population in Asia, Far and Middle East since the mid-1990s. One of the most widespread lineages established in poultry is the G1 lineage. This lineage has undergone further evolution and reassortment since its first detection in 1997 and G1-like H9N2 viruses still circulate. In this study we have investigated the susceptibility of quail and turkeys to the H9N2 G1- lineage prototype strain (A/quail/Hong Kong/G1/97). Contact transmission experiments were carried out in both avian species. Animals were infected oro-nasally with increasing doses of the virus (10 3 –10 6 EID 50 /0.1 ml) and sentinel birds were introduced 4 days post infection (pi) in each experimental group. Quail were more susceptible than turkeys, as they were readily infected with lower challenge doses. Interestingly, infection of turkeys was associated with worse clinical condition. Transmission was detected in both species. Quail infected with a dose less than or equal to 10 4 EID 50 transmitted the virus to the sentinels without showing any signs of disease. These findings reinforce the hypothesis that quail may ensure the perpetuation of H9N2 viruses in poultry, acting as a silent reservoir. ß 2013 Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +39 049 8084367; fax: +39 049 8084360. E-mail address: fbonfante@izsvenezie.it (F. Bonfante). 1 Both the authors contributed equally to this work. G Model VETMIC-6154; No. of Pages 7 Please cite this article in press as: Bonfante, F., et al., Susceptibility and intra-species transmission of the H9N2 G1 prototype lineage virus in Japanese quail and turkeys. Vet. Microbiol. (2013), http://dx.doi.org/10.1016/j.vet- mic.2013.03.014 Contents lists available at SciVerse ScienceDirect Veterinary Microbiology jo u rn al ho m epag e: ww w.els evier.c o m/lo cat e/vetmic 0378-1135/$ – see front matter ß 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.vetmic.2013.03.014